1. Field of the Invention
The present invention relates to silver halide photographic sensitive elements having dyed hydrophilic colloid layers.
2. Description of the Prior Art
In silver halide photographic sensitive elements, dyeing the photographic emulsion layers or other hydrophilic colloid layers so as to absorb light of a specific wavelength range has often been done.
When it is necessary to control the spectral composition of the light passing into the photographic emulsion layers, a dyed layer is generally provided at a position farther from the support than from the photographic emulsion layer. Such a dyed layer is called a filter layer. Where a plurality of photographic emulsion layers are present, the filter layer may be positioned between two of the layers.
Provision of a dyed layer, called an antihalation layer, between the photographic emulsion layer and the support or on the back of the support has been employed in order to inhibit blurring of images, that is, halation, caused by the phenomenon where rays scattered after or during passing through the photographic emulsion layer are reflected at an interface between the emulsion layer and the support or at the surface of the support opposite to that upon which the emulsion layer is coated back into the photographic emulsion layer again. In cases where a plurality of photographic emulsion layers are present, the antihalation layer may be positioned between two of the layers.
In order to prevent degradation of image sharpness caused by scattering of light in the photographic emulsion layers (this phenomenon is generally called irradiation), dyeing of the photographic emulsion layers has been employed.
Usually water soluble dyes are added to those hydrophilic colloid layers which are to be dyed. These dyes must have the following characteristics.
1. The dyes must have an appropriate spectral absorption corresponding to their use.
2. The dyes must be photochemically inert. Namely, they must not have an adverse chemical influence upon the silver halide photographic emulsion layers, for example, decrease the sensitivity, degrade the latent images or cause an occurrence of fog, etc.
3. The dyes must be decolored during photographic processings or must be removed by dissolving into processing solutions or in water used for washing and must not cause a harmful residual color on the photographic sensitive elements after processing.
Many attempts have been made by persons skilled in the art in order to find dyes which satisfy these requirements. There are, for example, oxonol dyes having a pyrazolone nucleus such as the dyes described in British Patent 506,385, oxonol dyes having a barbituric acid nucleus such as the dyes described in U.S. Pat. No. 3,247,127, other oxonol dyes as described in U.S. Pat. Nos. 2,533,472 and 3,379,533 and British Patent 1,278,621, hemioxonol dyes such as the dyes described in British Patent 584,609, styryl dyes such as the dyes described in U.S. Pat. No. 2,298,733, merocyanine dyes such as the dyes described in U.S. Pat. No. 2,493,747 and cyanine dyes such as the dyes described in U.S. Pat. No. 2,843,486.
Many of the dyes which are to be decolored in the processing of the photographic emulsion layers are decolored by sulfites (or bisulfites) present in a development processing solution or by such salts under alkaline conditions, which have been described in, for example, British Pat. 506,385.
Where the dyed layer is a filter layer or is an antihalation layer positioned on the same side of the support as the photographic emulsion layer, it is often necessary for that layer only to be dyed selectively and other layers not to be substantially dyed. If this is not so, the dyed layer not only causes a harmful spectral effect on other layers but also its effect as the filter layer or the antihalation layer is deteriorated.
There are many methods to dye selectively a specific hydrophilic colloid layer. However, the most commonly used method comprises incorporating a hydrophilic polymer having an opposite electric charge to the dye ion as a mordant in the hydrophilic colloid layer, by which the dye is present only in that specific layer due to an interaction between the mordant and the dye molecule (which is based mainly on absorption by means of electric charges but also on hydrophobic bonds). Polymers derived from ethylenically unsaturated compounds having a dialkylaminoalkyl ester residue described in British Patent 685,475, reaction products prepared by reacting polyvinyl alkyl ketone with aminoguanidine as described in British Patent 850,281, and polymers derived from 2-methyl-1-vinylimidazole as described in U.S. Pat. No. 3,445,231 are known as mordants. Where a method of mordanting using such polymers is used, when the layer to which the dye was added is brought into contact with other hydrophilic colloid layers in a wet state, a portion of the dye sometimes diffuses from the former layer to the latter layer. The diffusion of the dye depends upon not only the chemical structure of the mordant but also on the chemical structure of the dye used.
Where the above described high molecular weight mordants are used, residual color on the photosensitive elements easily occurs after photographic processings, and, particularly, after processing in which a shortened processing time is used. The reason for this is believed to be because the dye or reversible decolored products remain in the mordant containing layer, because the mordant still has a certain degree of bonding strength to the dye although the bonding strength of the mordant to the dye becomes fairly weak in alkaline solutions such as a developing solution. This also depends upon the chemical structure of the mordant and that of the dye.